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J. E. HILBISHL TELEPHONE SYSTEM.

APPLICATION man M^R.15.1915.

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UNITED STATES PATENT OFFICE.

JOHN E. HILBISH, OF LA. GRANGE, ILLINOIS, .A8-SIGNOR T0 KELLOGG SWITCHBOABD AN D SUPPLY COMPANY, 0F CHICAGO, ILLINOIS, A CORPORATION 0F ILLINOIS.y

TELEPHONE SYSTEM.

Bpeoioatlon of Letters Patent.

Patented Sept. 2, 1919.

Be it known t at I, JOHN E. HrLBrsH, a citizen of the United States of America residing in La Grange, county of Cook, and State of Illinois, have invented certaln new and useful Improvements in TelephoneSystems, of which the following is a spec1cation.

My invention relates to telephone systems in which link or trunk circuits are em loyed, and has to do more vparticularly wit manually operated link circuits of the so-called universal typefor interconnecting lines of different character, such as local battery and common battery lines.

One of the features of my invention is the provision of so-called instantaneous disconnect and recall for use with a cord circuit of the universal type, that is prior to the removal of the answering lug from the con nected jack should the sul scriber wish to recall, he may immediately `do so due to automatic means in thecord circuit that adjusts itself to place the line circuit of the recalling subscriber innormal condition as soon as the calling subscriber has signaled for discon-l nection.

Another feature of my invention is the provision of means whereby when connection is made between lines of one character, as between -common battery lines, automatic connection and disconnection of the opera- .toi-s circuit is provided giving so-called secret service, while when connection is established between lines of a dlfferent character such as local battery or magneto lines,

or between a local battery and a common battery line, it is necessary for the operator to operate a listening key in order to connect the oper'ators circuit with the cord circuit. I have also arranged' the cord circuit for use in extending calls over a trunk ,circuit to a second operators position at which position the trunk lcircuit terminates in a socalled threewire or threeconductor plug used for directly. establishing connection with called subscribers lines. I arrange the equipment of the trunk circuit associated with the second operators position in such a manner that the called subscriber is permitted to immediately recall even though the calling plug' remains connected to the jack ofr the called subscriber. When I use a universal cord circuit for extending trunking connections to a second operators positionfor connecting with a called subscriber of the common batte type, I provide automatlc rmgmg control ed by the operator atl the first operators position while when the universal cord circuit is used for directl extendmg connection to a magneto or ocal b attery line,I provide socalled manual rlngmg, which is directly controlled b -the oprator associated with the said cor circu1 For a better understanding of my inventlon, reference may be yhad to the accompanying drawing in which is shown a common battery substationAand a magneto substation B terminating` at the central oiice in line circuits L and L1, respectively. The common battery line circuit L comprises the usual line relay LR, cut-ofi' relay yCO, the multiple jack J, and line signals S. The line circuit as illustrated, is known as a multiple line lamp circuit in which a line lamp appears before each line jack so that when a call is initiated a signal appears1before each of the multiple line jacks so that any one of a number of operators may answer the call to the exclusion of the others. The magneto line circuit L1 comprisesa cut-oil:

relay CO1,` the drop signal DS, and .the line it is to be understood that a number of mul Y is actuated upon the insertion of a plug in a jack of a calling line, the said relay upon actuation connectlng the answering sleeve supervisory relay AS to the answermg lug of the cord circuit, and this operation oi) the relay AS connects the operators set O with' the said cord circuit. The relay AS being of low resistance shunts out the relay TE and should another operator attempt 'to seize the call, the relay AS of the cord circuit C will shunt out the relay TE of the second cord circuit attempting to seize the call, and therefore the operators set of the second cord will not be connected, due to the failure of the relay AS of the said second cord circuit to operate. The second operator, not receiving a response, knows that the call has been answered and therefore withdraws her plug. A switching relay SW is provided which is operated 4upon the actuation of the relay TE to connect the an' swering tip supervisory relay AT to the strands of the cord circuit. An answerlng magneto supervisory relay AM is provided adapted' to be bridged across the tip and ring conductors of the cord circuit to permit a calling magneto subscriber to give a disconnect signal. A disconnect magnet DM is associated with the relay AM and is energized to efface the supervisory signal AL after a calling magneto subscriber has given\ the disconnect signal. The relay DM upon energization also restores the armature of the relay AM to normal. A link disconnect relay LD is also associated with the answering end of the cord circuit C, and operates to immediately restore a calling common battery subscribers line circuit when the sub-y scrlber replaces his receiver, so that he can recall prior to the removal of the plug from the connected jack. The relay LD is also operated when a magneto subscriber replaces his receiver and operates the hand generator to give a disconnect signal so that his asso ciated line circuit is immediately restored to allow him to recall prior to the removal of the plug from its connected jack. At the calling end of the cord circuit I-provide a calling tip supervisory relay CT, and a calling sleeve supervisory relay CS, the two relays controlling the circuit of the combined calling and ringing supervisory lamp CL. A party-line ringing key RK is shown for connecting one of a plurality o f generators to the common generator lead 130 and for starting the automatic signaling of a common battery substation. A ringing control relay RD is also provided which is energized when any one of the ringing key plungers is actuated, the relay RD controls the energization of )an interrupter relay RI, which relay is intermittently energized and deenergized through the medium of an interrupter I. Manual ringing is also provided for signaling a called magneto substation, each time a ringing key plunger is fully depressed, the relays RD and RI energize and apply ringing current to the called line. Automatic listening and disconnect is pro- -vided when connection is established be- 'nection is established between two local bat The relays CM,1 and DM1 perform the f same functions at the calling end of the cord circuit as do relays AM and DM at the answering end of the cord circuit. The cord circuit C may be used for extending trunk'- ing connections and alsomay be `used for directly interconnecting local battery and common battery lines, that is, the calling plug CP may be used to directly establish connection with a subscribers line equipf ment.

The trunk circuit D as illustrated, is arranged to coperate with' the cord C for eX- tending trunking connections to a second operators board. The trunk jack TJ associated with the said trunk circuit is one of'a plurality of like jacks which appear before an operators position. The opposite end of the trunk circuit D terminates in a .trunk calling plug TCP for directly connecting to the multiple jacks of a called subscribers line equipment. The trunk circuit D is also provided with a supervisory lamp GL and a number of quick and slow acting relays,

the functions of which will be fully described hereinafter when a detailed Voperation of the equipment will be given.

To the right of the drawing I have shown a called common battery substation E termi-- nating in the line equipment L2. The substation E-and its associated line equipment is similar in all respects to thesubstation A and its` associated line equipment.

Having described in a general way the apparatus in the general embodiment of the preferred-form of my invention, I will now describe more in detail the operation of theA system as illustrated. y

Assuming now that the subscriber at the substation A initiates a call, the removal of the receiver at the substation operates the line relay LR to bring about the lighting of V the line signal S. The operator noting the lighted signal inserts the answering plug AI into Vthe jack J of the calling vline complet'- ing an energizing circuit for the high resistance test relay TE througlr the cut-off relay CO. This circuit extends from battery through the winding ofsaid test relay, the normal Contact 1 of the relay LD, the sleeve contacts of the connected plug and jack and through the windingof the cut-olf relay CO to ground. Upon the energization of the relay TE a multiple energizing circuit for the sleeve answering supervisory rela AS and the switching relay SW is establlshed. This circuit extends from battery through the windings of said relays, alternate contact 2 of relay TE, no rmal contact 1, sleeve .contacts ofthe connected plug and jack,

through the winding of the cut-,off relay CO A to ground. The cut-oli' relay CO energizinsg over this circuit eaces the line lamp Due to the low resistance nath brought about by including the relay A in circuit the high resistance test relay TE is shunted out and returns to normal. Should another operator attempt to seize the call, the answering sleeve supervisory relay of the cord circuit C prevents the 'test relay TE of the second cord circuit from operating to allow the energization of the relay AS of the second cord\ and thus prevents the second operator from -communicating with the calling subscriber.

The relay AS upon energizing, closes a locking circuit for itself traced from battery through relay AS, its alternate contact 3, contact 1, sleeve contacts of the plug and jack, through therelay CO to ground. A circuit for relay SW is also established when lrelay AS energizes traced from battery through the winding of the said relay, alter- `nate contact 3, normal contact 1, sleeve contacts of the plu and jack and through the -winding of re ay CO to ground. The

switching relay SW, upon energizing closes a circuit for the relay AT traced from battery through the lower winding of said relay, alternate contact 44, ring contacts of the connected plug and jack, through the suby station, tip contacts of the plug and jack,

alternate contact 45, through the upper winding of AT to ground, energizing the said relay to prevent the premature llghting of the answering supervisory lamp AL The closing of the alternate contacts 4 and 5 of the relay AS connects the operators set O to the cord circuit through the said alternate contacts, normal contacts 6 and 7 of the sleeve calling supervisory relay CS. The

operator now being connected to the cord,

circuit C ascertains the wants of the calling subscriber and assuming that it is the subscriber at the substation E that is wanted the connected operator now operates an orderwire key, (not shown, but well understood in the art) to communicate with the 'operator associated with the trunk ircuit D and repeats the number of the cal ed subscriber to -CP into the assigned trunk jack TJ. The insertion of the plug'lCl into the jack J2 closes a series energizing circuit for the cutoff relay CO2 of the linc'circuit L2 and the high resistance supervisory relay SR of the trunk circuit D. This circuit extends from battery through the high resistance relay SR, the normal Contact 8 of switching relay SW2, normal contact 9 of relay 100, normal contact 1l of relay 12, the sleeve contacts of the connected plug and jack through the winding of the cut-off relay CO2 to ground. The energization of the relay SR closes a circuit for the guard lamp GL traced from battery through the said lamp, to ground at alternate contact 13 of relay SR. The guard lamp GL remains lighted 1n case the operator at the cord circuit C inserts the calling plug CP into a trunk jack other than the one which has been assigned by the operator at the trunk circuit D. Upon inserting the calling plug CP into the assigned trunk jack T an energizing circuit is established for the switching relay SW2, traced from battery through the winding of the said relay, conductor 14, to ground at alternate contact 15 of the trunkj ack TJ. The energization of the relay SW2 opens the energizin circuit of the relay SR at contact 8, relay R denergizing opens the circuit of the' guard lamp GL at contact 13 and the effacement of the said signal notifies the operator associated with the trunk circuit D that the assigned trunk jack has been seized. A series energizv ing circuit for the cut-off relay CO2 and the sleeve supervisory relay CS of the cord circuit C, is also closed upon the insertion of the plug CP into the jack TJ This circuit extends from battery through the winding of the relay CS, the sleeve contacts of the connected plug CP and trunk jack TJ, conductor 16, the sleeve contacts of the connected plu TCP and jack J2, through the Winding of t e cut-oil' relay CO2 to ground. Upon the energization of relay CS its normal contacts 6 and 7 are interrupted to disconnect the operators set O from the cord circuit C. The relay SW2 upon energizing closes a circuit for the relay 10 traced from battery through the winding of the said relay to ground at alternate contact 46 of relay SW2. The re lay 10 upon energizing closes a locking circuit for itself traced from battery through the said relay, its alternate contact 47 to ground at normal contact 48.

A further result of the energization of the' relay CS of cord circuit C is -the closing of an energizing circuit for the switching relay SVVl, traced from battery through the winding of said relay, to ground at' alternate contact 17 of the relay CS. The switch-y ing relay SW1 upon energizing'v places the calling tip supervisory relay CT into operative relation with the cord circuit C to be energized upon the response of the called subscriber. A circuit for the supervisory lamp CL is also closed upon the energization of the relay CS, traced from battery through said lamp, normal contact 18 of relay RD, normal contact 19 of relay CT, alternate contact 20 of relay AS to ground at alternate contact 17. The glowing of the calling lamp CL notifies theoperator at the cord circuit C that the trunk operator has inserted the trunk plug TCP into the jack of the called line and also notilies her that she should now depress one of the ringing key plungers to signal the called subscriber. The operator at the cord circuit C next depresses the proper ringing plunger of the ringing key RK to ring the call-bell of the called subscriber at the substation E. When the ringing key RK is in its fully depressed position the common contact sprmgs 21 and 22 of the ringing key assume their alternate position closing an energizing circuit for the ringing control relay RD, traced from -battery through the winding of the said relay to ground at alternate contact^21 of the said springs. When the vpressure is released from the depressed plunger it assumes an intermediate position allowing the springs 21 and 22 to assume their normal position but keeping the selected generator connected' to the common conductor 130. The ringing control relay upon energizing, closes a locking circuit for itself independent of springs 21. This circuit extends -from battery through the winding of said relay, conductor 23, alternate contact 24: of the relay SW1,

alternate contact 25 of relay RD, normalv contact 26 of relay LD, conductor 27, normal contact 19 of relay CT, alternate contact 2O of relay CS to ground at alternate contact 17. A further result, due to the energization of the relay RD, is the eifacing of lamp CL and the closing of an energizing circuit for the interrupter relay RI. The circuit for the ,interrupter relay RI eX- tends from battery through the interrupter I, normal contact 22 of the common springs, the winding of the said relay RI, alternate contact 18 of relay RD, normal contact 19 of relay CT, alternate contact 20 to ground at alternate contact 17 of relay CS. The relay RI is thus intermittently energized and denergized causing ringing current to be applied to the called line through its alternate contact 30. The circuit for the said ringing current extends from the ungrounded pole of the generator, closed contact of the ringing key, alternate contact 30 of relay RI, tip contacts of the connected plug and jack, conductor 31, tip contacts of the connected plug TCP from the jack J2, through the condenser and .call bell of the called substation E, the ring contacts of the jack J2 and plug TCP, conductor 32, ring contact of the jack TJ and plug CP' through the alternate contact 33 of relay RI to ground. The call bell at the called substation is thus intermittel rung until the called subscriber answers. he subscrlber at the called substation E in, response to the call v signal removes his receiver from the switchhook thus closing an energizing circuit for the callingtip supervisory relay CT traced from battery through the lower winding of the relay CT, alternate contact 35 of relay SW, normal contact 33, the ring contacts of the connected plug CP and jack TJ, conductor 32, ring contacts of the connected plug TCP and jack J2 through the substation, the tip contacts of the connected plug and jack, conductor 31, tip contacts of the jack TJ and plug CP, normal contact 30, alternate contact 36 of relay SW1 through the upper winding of the relayl CT to ground. The energizing of the relay CT opens the locking circuit for the relay RD at its normal contact 19 causing the deenergization of the said relay RD, which relay upon energizing, opens the circuit of the relay RI thereby preventing ringing current from being applied to the called line. Thel subscriber at the calling substation A and the subscriber at the called .substation E may now carry on conversation over the heavily marked talking conductors.

contact 37, alternate contact 38 of relay SW,

conductor 39, alternate contact 40 ofl relay AS to ground at alternate contact 17 of relay CS. A further result of the denergizing of relay AT is the closing of an energizing circuit through the link disconnect relay LD traced from battery through the winding of the said relay, normal contact 37 of relay AT, alternate contact 38 of relay SW, conductor 39,'alternate contact 4:0, conductor 4:1' to ground at alternate contact 17 of relay CS. The closing of alternate contact 1 of relay LD maintains 'the energizing circuit for the relay AS and SW, the circuit for relay AS being traced from battery through the said relay, alternate contact 3 of said relay, alternate contact 1 of relay LD` alternate contact 40 of relay AS to ground at alternate contact 17 of relay CS and the energizing circuit for relay SW is traced from battery through the relay SW alternate contact 3 of relay AS, alternate contact 1 of relay LD, alternate contact 40 of relay AS to ground at alternate contact 17. The energization of the link The clos-` disconnedt relay LD opens the circuit for the cut-oil` relay CO of the line circuit L 'at the contact 1 of the said relay LD allowing gizing circuit for the calling supervisory lamp CL traced from battery through the said lamp, normal contact 18 of relay RD, normal contact 19 of relay CT to ground at alternate contact 17. The operator noting the two lighted supervisory slgnals and CL knows that conversation has terminated and withdraws plug AP from the jack J and the calling plug .CP from the trunk jack TJ.

Should' the calling subscriber wish to recall before the answering and calling plugs have been removed from their respective jacks, the subscriber removes his receiver which again brings about the energization of relay LR to light the line signals S in the same manner as hereinbefore described. Thevcall may now be seized by'any idle operator and extended in the Same Vmanner as hereinbefore described. Returning now to the removal ofthe answeringl and calling lugs AP and CP from their respective Jacks, the removal of the calling plug CP from the trunk jack TJ allows the calling supervisory relay CS to denergize. The denergizing-'of relay CS opens the circuits of relays LD, SW and AS and of the supervisory lamp AL at the spring 17, thus allowing the equipment at the answering end of the cord circuit to be restored to normal. The switching relay SW1 is restored to normal by the opening of its circuit at the contact springs 20 when the relay CS denergizes thus restoring to normal the equipment associated wit-h the calling end of the cord circuit. The removal of the plug CP from the trunk jack TJ also opens the energizing circuit for the switching, relays SW2 of the trunk circuit D at the normal contact 15 of said trunk jack. The relay SW2, upon denergizing, closes an energizing circuit for the relay 100 traced from battery through the winding of the said relay and alternate contact 50 of the relay 10 to ground at normal contact 46. Upon the energization of the relaylOO an energizing circuit for the relay 12 1s establlshed, traced from battery through the winding of the said relay to ground at alternate contact 51 of relay 100. The relay 12 upon energizing closes a locking circuitfor itself, traced from battery through the winding of the said relay, its-alternate cont-act 11, the sleeve contacts of the connected plug TCP and jack J 2 through the winding of the cutoif relay CO toground. Relay 12 upon energizing,causes the combined guard and su- 4 pervisory 1am GL to again glow due to the closure lo the alternate contact 48 to ground, thus noti ing theo erator that the connected plug o the co circuit C has been removed from the trunk jack TJ. The relay 12 is of comparatively high resistance, and therefore allows the cut-ofi' relay CO2 to denergize which allows the line circuit L2 to restore to normal. The operator noting the lighted lamp CL removes the plug TCP from the jack J2 allowing the relay 12 t0 restore. The restoration of the relay 12 eifaces the lamp GL by opening the contact 48, the apparatus ofthe trunk circuit D being restored to normal places the said trunk circuit in condition to set up other connections. Should the subscriber at E wish to recall he may do so even though the operator has neglected to remove the plug from the connected jack due to'the denergization of relay COz of line circuit L2 which allows the line circuit `L2 to. restore to normal. The removal of the receiver at the substation will light the line signal S2.

Assuming now that the subscriber at the magneto substation B wishes to initiate a call, the subscriber thereat will operate his hand generator to operate the drop signal DS of the line circuit L1 and then remove his receiver from itsy switch-hook. The operator noting the actuated drop signal linserts' the answeringplug AP into the jack J1 of the calling line, thus closing a series energizing circuit for the high resistance test relay TE and the cut-oil:` relay CO1.. This vcircuit extends from battery through the winding of relay vTE, normal contact l yof `relay LD, the sleeve contacts Vof the connected plug and jack through the winding of cut-ofil relay CO1 to ground. The operation of relay TE and the closing of its contact 2 connects the relays AS and SW in series with relay CO1 but because of the comparatively high resistance of the said lrelay CO1, the relays AS and SW are prevented from operating. The failure of re lay AS to operate prevents the operators set O from being connected to the cord cir-v cuit, the operators listening key LK must be operated to 'connect the operators set O to the cord circuit to ascertain the wants of the calling magneto line. IThe failure of the switching relay SW to operate prevents the connection of the relay AT to the answering end of the cord circuit. Now assuming, that it is the subscriber at the common battery substation E that is wanted, the operator presses an orderwire key, (not shown), to communicate with the operator associated with the trunk circuit D. The number of the called subscriber is repeated to the operator associated `with the trunk D and the operator thereat assigns a trunk as previously described. The operator at C now plugs into the assigned trunk jack and actuates the ringing key RK. The operation of the apparatus of the ,cord circuit C at its calling end and that `of the apparatus of the trunk circuit D is the same as that described 'in lconnectionwith the description gizing'the relay AM. This circuit extends Y from the generator at the substation, the tip contacts of the connected plug and jack, the normal contact 52 of relay LD, normal contact 45 of relay 'SIW through the winding of the relay AM, normal contact-44 of relay SW, normal contact53 of relay LD, ring finished conversation.

contactsof the connected plug and jack',

back to the generator. The disconnect'current energize's the relay AM and causes the attraction of its armature 54 causing the Vlocking contact 55 to hold the armature 54 in its attracted position and to close the alternate contact 55 thus bringingabout the lighting of the answering supervisory lamp AL, traced from battery through the lamp to ground at alternate contact 54. A further result due to the operation of the relay AM is the operation of the link disconnect relay LD, traced from battery through the winding of the. said relay to ground at alternate contactV 55. The operation of the link dis-4 connect relay LD opens its Anormal contact l'jthus bring" about the denergization of the cut-oil:l relay CO1 and the test relay TlE. The cut-olf relay C()1 upon denergiz` ing again places the dropsignal DS of the line circuit L1 in condition to be againv operated by current from the hand generator of the substation B. The lighted signal AL notilies the operator of the cord'circuit C that the subscriber at the substation B has e subscriber at the called substation E having replaced his re ceiver, brings about the operation of the apparatus at the calling end of the cord circuit as previously described to light the calling supervisory lamp CL and the operator noting vthe two lighted signals knows that the two subscribers have linished conversation. Should the subscriber B wish to recall he simply operates his hand generator the same as before thus causing the drop DS to operate. The closing of the contact'55 of relay AM having lighted the signal AL and the signal CL having been lighted by the replacing of the receiver at the called substation, the operator noting the two signals removes the plugs AP and CP from the connected jacks. The removal of the plug namens CP brings about the restoration .of the appara-tus associated with the calling' end ot the cord circuit and with the trunk circuit D as previously described. The removal of the plug AP does not affect the relay LD or lighted signal AL; therefore the operator momentarily operates the listening key LK closing the contact 60 which establishes an energizing circuit for the disconnect'magnet DM being traced from battery through the said magnet to ground at Contact 60. The magnet, upon energizing, attracts its armature 61 and the extension 62 of the armature l61 lifts the contact 55 outof locking engagement with the armature 54 thereby opening the circuit for the relay LD and ei'acing the signal AL. The apparatus of the cord circuit C is now at normal and the said cord is available for other connections.

We will now assume that the subscriber at substation B desires connection with another local battery substation, not shown, but I similar to substation B. The subscriber at B operates the drop signal DS the same'as hereinbefore described and the operator plugs into the jack J1 with the answerinor plug AP and operates the listening key -L to learn the wishes ofthe calling subscriber. The operator upon learning the subscriber desired, takes the calling plug CP and plugs into a Jack similar to jack J1 (not shown) and operates her ringing key to signal the called subscriber. Upon insertin theI plug CP-into the jack of theA called su criber a circuit is closed through the calling supervisory relay CS in series with the .cut-oil'I relay of the called line. the called cut-oli relay is such that it does no t permit sucient current, to flow to operatlvely energize the calling supervisory relay CS. The operator'next signals the called Subscriber b operating the ringing key RK. Each time t e springs 21 and 22 make contact with their alternate contacts, circuits are closed through the ringing contact, rela RD and then through the ringing relay R The circuit for the ringing control relay RD extends from battery through'the said .rent to the called line.

A fter the conversation has terminated the calllng subscriber replaces his receiver and 'operates the hand generator causing the same operations to take place at the answering end of the cord circuit as hereinbefore described. .The called subscriber replaces his receiver and operates his hand generator, thus causing vthe calling magneto supervisory relay CM1` to be operated. The

ioo

The resistance of l relay CMBupon operating closes a lcircuit through thecalling supervisory lamp CL and its own armature 162 is mechanically locked by thearmature of the disconnect m et DM. The operator upon noticing bot superviso li hts glowing presses the liste key t us connecting her head Set to e strands of the cord circuit C and at .the same time closing circuits through the disconnect magnets DM and DM1 at the springs 6D. The disconnect magnets DM eration of the apparatus that takes place when the cord circuit C is used to establish direct connections between a calling local battery or a calling common battery subscriber and a called common battery subscriber it isreadily seen that the operation of the apparatus of the cord circuit C is practically the same as when it is used for establishing trunking connections. f

While I have shown the line circuit L1 as that of an individual subscriber, it is apparent that, it may be the line apparatus associated with an incoming toll line from a distant toll board, and that the cord cn'- cuit C may be used for directly connecting` together toll lines or toll subscribers and may also be used'for extending connections from toll lines to local operators positions by ,means of trunking circuit D, the local operator then completing the connection with the called subscriber by inserting the tip calling plug TCP into the jack of the called subscriber.

In working out my invention I have employed preferred circuit arrangements all of which go to make an eliicient operating system, but it4 is to be understood that I contemplate other circuit arrangements. Furthermore many chan es or modifications of the system illustrate will readily occur to those skilled in the art and therefore I do not desire to be limited to the arrangement shown and described but aim to cover all such changes and modifications as come within the spirit and scope of the appended claims.

Having described my invention, what l claim as new and desire to secure by United States Letters Patent is:

1. vA telephone system including local battery and'common battery lines, connecting terminals for said lines, a universal link circuit for interconnecting said lines, a test relay .associated with the answering end of said llnk c1rcu1t, and means including said test relay and said answering terminal for determinin whether a call initiated over one of sai common battery lines is in an answered or an unanswered condition.

2. A telephone system including local battery and common battery lines, connecting terminals for said lines, universal link circuits having manually controlled answering terminals or connection with said connectingl terminals when answering calls initiated over said lines, and means for preventing theoperative association of more. than one of sald answering terminals with the terminals of any one of said-common battery lines at the same time when answering a call therefrom.

3. A telephone system including a plurality of common battery and local battery lines, a plurality of terminals for said lines located at the central ollice, operators universal link circuits for interconnecting said lmes, and means whereby any one of theV said link circuits may be connected to one of said common battery lines asa calling line tothe eYclusion of the remaining link circuits.

4. A telephone system including common battery and local battery lines, a universalv cord circuit provided with terminal plugs for interconnecting said lines, means whereby when a calling one of said lines signals for disconnection the line is rendered available for recall even though the answering plug of said cord circuit has not been removed from the jack of the calling line.

5. A telephone s stem including local battery and common attery telephone lines, a y

universal cord circuit lprovided with an answering terminal adapted to be connected with the line jack or any one of said lines, and means controlled by the subscriber at a calling substation for operatively disassociating the said cord circuit from the said calling line.

6. A telephone system including common battery and local battery lines, an operators universal link circuit provided with a terminal for use in interconnecting said lines, means ;for operatively disassociating the terminal of said link circuit from the line circuit of a called one of said lines even though the said terminal remains in the jack of the line.

7. A telephone system including common battery and local battery lines, a universal cord circuit provided with a terminal for interconnecting said lines, means forpoperatively disassociating a called line from the said terminal so that the called line may immediately recall even though the said termmal remains connected to the jack of the said called line.

8. A telephone system including common battery and local battery subscribers lines, a universal cord circuit for interconnecting anddisconnecting an operators circuit when said cord circuit 4is employedl to yconnect lines of. one of said characters, means for rendering said connecting and disconnecting means inoperative when a connection is` between lines of a like character but of a differ- .ent one of said characters, 'and means for.

rendering said connecting means inoperative when, connection is between a line of onecharacter and a line of another character.

10. A telephone system including common battery and local battery lines, a universal cord circuit for interconnecting said lines, an operators listening key for said cord circuit, automatic means in said cord circuit for. connecting and disconnecting an operators circuit and for rendering the saidlistening key inoperative when connection is extended between lines of vone of said characters, and means for rendering the said connecting and disconnectingV means ino erative and for renderin said listening {ey operative to connect sald operators circuit when connection is extended between lines of a like character but of a diii'erent one of said characters.

`11. In combination with a calling twoconductor magneto telephone line connected to a plug ended cord circuit lat the central exchange, means whereby when the subscriber signals for disconnect-ion the said line circuit is available for recalling before the plug is removed from the saidI line.

12. A telephone system including local battery vand common battery lines, a universal cord circuit provided with a plug end adapted to interconnect the said lines, and means controlled by a calling one of said subscribers when said plug is -connected to said calling line for operatively disassec'iating the said Aplug and said line so that the said subscriber may recall.

13. A telephone system including common battery and local battery telephone lines, connecting terminals for said lines located at a central oiiice switchboard, operators universal link circuits including means whereby any one of said link circuits may be connected to a terminal of a calling one of said common battery lines when answering a -call therefrom to the exclusion of the remaining link circuits.

14,. A telephone system including common battery and local batteryflines, connecting terminals for said lines, universal link cir cuits for interconnecting said lines, manuallyr operated answering terminals for said link circuits for connection withv the said line terminals, and means to prevent operative association of more than one answering terminal with the connecting terminals of any one of said common battery lines.

15. -A telephone system including common battery and local battery lines, an operators universal link circuit provided with al terminal for use in interconnecting saidlines, means for operatively disassociating the terminal of said link circuitfrom the line circuit of a calling one of said lines even though thesaid terminal remains in the jack of said calling line.

1'6. A telephone system including common battery and local' battery telephone lines, an operators universal link circuit for interconnecting saidlines, a manually controlled answering terminal for said link circuit, means for operatively disassociating the said link circuit from the line circuit of a calling one of said lines prior to the removal of said answering terminal from the jack of said line.

17. A telephone system including common battery and magneto telephone lines, a uni-v versal link circuit for interconnecting said means for disassociating said link circuit from the line circuit of a calling one of said lines prior to the disconnection of said link circuit terminal from the answering terminal of said line.

18. The combination with a two conductor calling magneto telephone line connected to a plug ended link circuit at a central exchange, of means controlled over the two conductors of the telephone line in series when the subscriber signals for disconnection for rendering the line circuit available for recall prior Ato thc disconnection of the plug from the said line.

19. A combination with a calling magneto telephone line connected to a plug ended link circuit at the exchange, of meansl whereby when the substation upon said line operates the magneto for disconnection tbe line is available for recall prior to the withdrawal of the link plug.

20. A telephone system con'xprising a twoconductor magneto telephone line terminating in a connecting jack at the central ottiee switchboard, an opcrators link circuit having a manual answering terminal for cxtcnding the circuit of said line by way ot' said jack, and means responsive t0 an operation of the magneto at the substation of said line for operatively disassociating said link circuit from said line.

21. The combination with a magneto telephone line connected to a plug ended link circuit at the central exchange, of means whereby Iwhen the substation on the said line signals :for disconnection the said link circuit is operatively disassociated from the liiie, and operator controlled means for permitting a reassociation of the link circuit and the line prior to the withdrawal of said link plug.

22. The combination with a two-conductor magneto telephone line connected to a plug ended link circuit at the exchange, of means whereby when the substation on said line signals for disconnection the link circuit is operatively disassociated from the conductors of the telephone line, and means for again uniting the said telephone line and the said link circuit prior to the withdrawal of the said link plug.

23. In a telephone system, a subscribers magneto telephone line, a plug ended link circuit adapted to be connected to said line, and means responsive to an operation of the magneto at the substation of said line for o eratively disconnecting the said line and link circuit prior to a withdrawal of said link circuit plug.

24. In a telephone system, a subscribers magneto telephone line, a plu ended link circuit adapted to be connecte to said line, means ,responsive to an operation of the magneto at the substation of said line for operativel disconnecting the said line and link circuit, and means for connectin said line and link circuit prior to the with rawal of said plug.

25. A telephone system including common battery and magneto telephone lines, a universal link circuit for interconnecting said lines, means under the control of the substation of one of said common battery lines for disassociating said link circuit from the said line whereby the line is rendered available for recall, and means for permitting a second plug ended link circuit to seize a recall from said line before the withdrawal of the answering plug of said first link circuit. y

26. A telephone system including common batte and magneto telephone lines, universal link circuits for interconnecting 27. A telephone system including a twoconductor magneto telephone line, a link circuit provided with a terminal for connection to said line, and means responsive to an operation of the magneto at the substation of said line for operatively disassociating said line from said link circuit, by energizing a relay to disconnect the strands of said link circuit from said telephone line while maintaining said terminal in association with said line.

28. A telephone system including local battery-and common battery telephone lines, a universal cord circuit provided with an answering terminal for connection with said lines as calling lines, and means controlled by the subscriber at the substation of one of said calling lines for operatively disassociating said calling line from said cord circuit. f

29. A telephone system including both local battery and common battery telephone lines, va universal link circuit provided with an answering terminal for connection to said lines as calling lines for extending connections therefrom, and substation controlled means controllable from the substation of a calling one of said lines for operatively disassociating said line from said link circuit.

30. A telephone system including both local battery and common battery telephone lines, a universal link circuit provided with an answering terminal for connection to said lines as calling lines for extending connections therefrom, and substation controlled means controllable from the substation of a calling one of said lines for operatively disassociating said line from said link circuit prior to the disconnection of said answering terminal from said line.

31. A telephone system including a twoconductor magneto telephone line, a link circuit provided with a terminal for connection to said line, inductive means for said link circuit, a relay for o eratively disassociating said link circuit om said telephone line by opening up the strands of said link circuit between said terminal and said inductive means, and means responsive to an operation of the magneto at the substation to operate said relay.

32. A telephone system including a twoconductor local battery telephone line, a link circuit provided with a terminal for connection to said line, inductive means for said link circuit, a relay for o eratively disassociating said link circuit om said line by disconnecting said terminal from said inductive means, means controlled over said local battery telephone line for operating said relay to cause said disassociation.

33. A telephone system including a magneto telephone line provided with a terminal, a link circuit provided with a terminal for connection to said telephone line via said terminals, and a relay for said link said subscribers telephone line while permitting said terminals to remain connected'.

34. A telephone system including -a twoconductor magneto telephone line, a link circuit provided with a connection plug for 'connecting said telephone line to said link circuit, electromagnetic means for said link circuit under substatlon control for operatively disassociating said link circuit from the'strands of said link circuit, electromagnetlc means for sald llnk c1rcu1t responsive 'to an operation of the magneto at the substatlon of said telephone line for operatively 2o disassociating said telephone line from said llnk circuit by opening up the strands of the link circuit between said inductive means and said plug.

Signed by me at Chicago in the county of 25 Cook and State of Illinois,

in the presence of two witnesses.

JOHN E. HILBISH.

Witnesses G. A. YANooHowsKI, B. OBRmN. 

